Chapter 1 Introduction IPmux-1/1E Installation and Operation Manual
1-16 Functional Description
Frame Format The Ethernet frame sent by the IPmux-1 is a UDP datagram that transfers E1/T1
payload bytes over IP over Ethernet (UDP payload + UDP header + IP header +
Ethernet header). The UDP payload size depends on the connection mode:
• Static mode: The UDP payload size is equal to TDM bytes per frame
(TDM bytes/frame configuration).
• Dynamic CAS mode: The maximum UDP payload size depends on the
number of configured time slots and is equal to:
[(TSA + 4) x (number of configured timeslots)] + 4]
where TSA = Active timeslot bytes in frame
Active timeslot bytes in frame are the number of bytes per timeslot that are passed
per Ethernet frame.
An Active timeslot is one where a call is detected by monitoring CAS.
The UDP payload size is not fixed–it depends on the number of active time
slots:
[(TSA + 4) x (number of active timeslots)] + 4]
• CESoIP mode: The UDP payload size is equal to:
[(Configured Packet Delay) x (number of configured timeslots) x 8] + 12
Table 1-2 specifies the structure of the different headers, special fields, and the
payload in the Ethernet packet.
MAC IP UDP Pa yload
Figure 1-15. TDMoIP Frame Structure
Note